Liquid Lens Curvature Control via Integrated Capacitance Sensing
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Solution Overview
Problem
Existing camera modules with liquid lenses face challenges in accurately recognizing and controlling the movement and shape of the liquid lens interface for focal length adjustment, leading to inefficiencies in autofocus and camera-shake correction, and increased size and power consumption due to separate lens-driving devices.
Innovation Solution
A lens curvature variation apparatus that includes a liquid lens with individual electrodes, a driver applying voltage, sensor units sensing capacitance changes, and a control unit to accurately control the lens curvature based on sensed capacitance, reducing the need for multiple AD converters and minimizing noise during sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a liquid lens is used to adjust focal length electrically, then the size and power consumption are reduced compared to mechanical lens modules, but the accuracy of recognizing and controlling the liquid lens interface movement is insufficient
Solution Approach 1:
The patent merges the sensor unit, multiplexer, AD converter, and control unit into a single integrated control circuit that directly monitors capacitance changes at the liquid lens electrodes. This integration enables accurate interface movement detection without requiring separate complex measurement systems, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent implements a feedback mechanism where the control unit continuously monitors capacitance changes at the electrodes, determines interface curvature based on these changes, and adjusts the driving voltage accordingly. This closed-loop feedback system enables accurate real-time control of the liquid lens interface movement, improving measurement precision while keeping the control circuit manageable through systematic feedback processing.
2Measurement precision
If multiple AD converters are used to sense each electrode individually, then the measurement precision is improved, but the device complexity and cost increase
Solution Approach 1:
The patent employs a single multiplexer that can sequentially connect different electrodes to a single AD converter, enabling one AD converter to perform multiple sensing functions across different electrodes. This multi-functional approach maintains measurement precision by allowing sequential capacitance measurement of each electrode while significantly reducing the total number of AD converters required, thus lowering device complexity and cost.
Solution Approach 2:
The patent uses periodic sequential scanning of electrodes through the multiplexer, where the control unit periodically switches between different electrodes to measure capacitance changes. This periodic action allows a single AD converter to repeatedly measure different electrodes in sequence, achieving comprehensive measurement precision without requiring simultaneous multiple AD converters, thereby reducing device complexity.
3Measurement precision
If a separate lens-driving device is used to control the liquid lens, then the control accuracy is improved, but the overall size and power consumption of the camera module increase
Solution Approach 1:
The patent integrates the lens-driving device functionality directly into the camera module's existing control circuitry by merging the sensor unit, multiplexer, AD converter, and control unit into a single integrated circuit. This consolidation enables accurate liquid lens control without requiring a separate dedicated driving device, thus maintaining control accuracy while significantly reducing the overall camera module size.
Solution Approach 2:
The patent designs the control circuit to perform multiple functions: monitoring capacitance changes, determining interface curvature, calculating required voltage adjustments, and driving the liquid lens electrodes. This multi-functional approach eliminates the need for a separate dedicated lens-driving device, achieving accurate control while minimizing the camera module size by consolidating all necessary control functions in a single integrated circuit.
4Speed
If the sensing operation is performed continuously, then the response speed is improved, but the noise from switching elements interferes with the sensing accuracy
Solution Approach 1:
The patent implements periodic sensing operations synchronized with the switching element operation cycles. The control unit performs capacitance measurements at specific time intervals when the switching elements are in stable states, avoiding interference during switching transitions. This periodic sensing approach maintains rapid response capability while ensuring measurement precision by timing the sensing operations to avoid noise interference from switching elements.
Solution Approach 2:
The patent performs preliminary stabilization of the switching element state before initiating the sensing operation. The control unit waits for the switching element to settle into a stable state (either fully on or fully off) before measuring capacitance changes. This preliminary action ensures that the sensing operation occurs under noise-free conditions, maintaining both rapid response speed and high measurement precision by preventing switching transients from interfering with the capacitance measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables quick and accurate curvature variation of the liquid lens, improving autofocus and camera-shake correction performance while reducing the camera module's size and power consumption, and lowering production costs by integrating components into a single chip.
Implementation Method 1
sensor units connected to each of the plurality of switching elements, and sensing an interface of the liquid lens that changes based on the voltage
Data Source
AI summary
A lens curvature variation apparatus according to an embodiment includes: a liquid lens including a common electrode and a plurality of individual electrodes; a lens driver applying a voltage to the common electrode and the plurality of individual electrodes; a plurality of switching elements connected to each of the plurality of individual electrodes; a plurality of sensor units connected to each of the plurality of switching elements, and sensing an interface of the liquid lens that changes based on the voltage; a multiplexer (MUX) connected to the plurality of sensor units, and sequentially outputs an analog signal corresponding to the interface output from each of the plurality of sensor units; an AD converter that converts the analog signal sequentially output from the MUX into a digital signal to output; and a control unit controlling the lens driver based on the signal output from the AD converter.